Oops. A new promotional poster made an appearance in a store at T-Mobile’s German headquarters, where it confirmed the existence of a Nokia Windows Phone with a 3.7-inch display and Nokia’s Drive navigation service.

The poster was up only briefly, but a quick-thinking tipster snapped a few shots and fired them off to WinRumors. After running it through a quick and dirty Google translation, the poster’s copy mentions that Nokia Drive for WP7 includes a 3D navigation display like its MeeGo cousin, and support for voice control.

Thrilling, no? Of course, that’s not all the poster had in store for us. Further down in the description, it makes mention of a device packing a 3.7-inch curved AMOLED display.

Nokia’s fabled Searay handset reportedly bears quite a resemblance to the company’s N9, but whether or not it shares the device’s 3.9-inch display is still in the air. If it does though, then these marketing materials may refer to another Nokia device that was accidentally outed earlier this week.

If the terms and conditions of a Microsoft Canada contest are to be believed, then Nokia has at least one more Windows Phone in the pipeline. Rumors of a handset called the Sabre can be laid to rest, as the contest’s fine print seems to back up the device’s existence. Details are pretty much non-existent at this stage, but WPCentral ruminated that the Sabre would have a 3.7-inch display when they first caught wind of it last month.

The matching screen sizes could be a complete coincidence, but it’s also possible that Nokia’s Sabre is farther along then we thought. The fact that Microsoft has since pulled the offending wording from the contest rules only makes the Sabre look more official. With Nokia’s Windows Phones poised to launch before the year is out, they’ll hopefully come forward with details sooner rather than later.